Method of covering a member

ABSTRACT

A recoverable tubular article comprising an elastomeric sleeve held in an expanded or extended condition and capable of recovering to its unexpanded condition of smaller diameter upon the removal of an outer restraint, an outer restraint, essentially tubular in configuration, bonded to said elastomeric sleeve, said restraint and said bond between the sleeve and the restraint being sufficiently strong to retain the elastomeric sleeve in its expanded condition under ordinary conditions of storage and said restraint being capable of being segmented and peeled from said elastomeric sleeve to permit said sleeve to recover to its original state.

This is a divisional of application Ser. No. 586,901 filed June 16,1975, now U.S. Pat. No. 4,338,970.

BACKGROUND OF THE INVENTION

Heat recoverable sleeves have found wide utility in many applications.Thus, heat recoverable sleeves are used as insulators for electricalconductors, particularly at areas where splices are formed in theelectrical conductors. The sleeves have been particularly successfulbecause they allow rapid and uniform application of an insulatingcovering. Typically, an electrical conductor which is to be spliced orrepaired first has an expanded heat recoverable sleeve placed over theconductor. The repair is then made and the sleeve is put in place overthe splice and recovered by the application of heat. Such methods haveproven quicker, more convenient, and more reliable than prior methodssuch as taping and vulcanizing.

A disadvantage in use of heat recoverable sleeves is that a heat sourceis necessary for the recovery. Suitable heat sources include torches andhot air guns. In some cases, it is undesirable to use torches because ofthe danger of fire being started by the open flame. In other situations,working conditions are so cramped or otherwise difficult that it is notconvenient to place a heat source such as a torch or heat gun close tothe sleeve which is to be recovered. The use of heat-recoverable sleevesmay also be undesirable where the substrate on which the sleeve is to beshrunk is temperature sensitive.

Various methods of recovering sleeves without the application of heathave been proposed. In particular, various types of expanded sleeveswith internal restraints holding the sleeves in the expanded conditionhave been disclosed. One such sleeve comprises an expanded sleeve heldin the expanded state by a cylinder of ice as disclosed in U.S. Pat. No.3,319,328. In actuality, such a sleeve is also a heat-recoverable sleevebecause it requires a minimal amount of heat to melt the ice and allowthe sleeve to recover. However, the heat necessary is so low that such asleeve is not normally considered a sleeve requiring an application ofan outside heat source. Another type of sleeve having an internalrestraint is that described in U.S. Pat. No. 3,515,798 wherein a rigidremovable mechanical insert holds the sleeve in the expanded conditionuntil the insert is removed.

In general, all of the proposals for making recoverable sleeves which donot require heat have involved internal restraints, configurations whichplace a restraint between the substrate and the internal surface of thesleeve or involve contacting the internal surface of the sleeve withsome foreign material. Such configurations present various problems.

Frequently, it is desired to coat the inner surface of a recoverablesleeve with a sealant or adhesive material. Configurations of heatrecoverable sleeves with internal restraints often make the use of suchan internal coating difficult or impossible. Furthermore, the impositionof an internal restraint between the sleeve and substrate makes fittingof the sleeve over the substrate difficult and reduces the range ofsubstrate sizes which the sleeve can be fitted over.

SUMMARY OF THE PRESENT INVENTION

The present invention provides a recoverable sleeve which does notrequire the application of heat for recovery and which is held in therecoverable position by an external restraint. The extended sleeve isheld in the position by a restraint bonded to the sleeve. Recovery ofthe sleeve is achieved by weakening the sleeve sufficiently to allowrecovery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the article of the invention in positionfor being shrunk down about a substrate.

FIG. 2 is a perspective view of the article of the invention wherein therestraint has been segmented by fracturing.

FIG. 3 is a perspective view of the recoverable sleeve after it has beenrecovered onto a substrate.

FIG. 4 is a perspective view of a recoverable sleeve wherein therestraint can be segmented and peeled along scored lines.

FIG. 5 is a perspective view of the sleeve after it has recovered onto asubstrate.

DESCRIPTION OF PREFERRED EMBODIMENTS

The Recoverable Sleeve

An article according to the present invention is shown in FIG. 1. It canbe seen that the article comprises an outer rigid restraint 1 and aninner recoverable tube 2. The recoverable tube or sleeve is preferablyan elastomeric sleeve. However, recoverable sleeves of other materialssuch as metallic split cylinders in tension may be used. The elastomericsleeve must be capable of being stretched or extended radially to adimension from which the sleeve can recover upon the removal of therestraint holding it in the stretched or extended condition.

For the elastomeric sleeve, virtually any desired material possessingelastomeric recovery properties may be used. The elastomeric materialshould be one which does not exhibit a substantial permanent set ordecrease in recovery on storage. Suitable elastomers include materialssuch as natural and synthetic polyisoprenes, cis-polybutadiene,styrene-butadiene rubber (SBR), butadiene-acrylonitrile rubber,polychloroprene (neoprene), butyl rubber, polysulfide, silicone rubber,urethane rubber, polyacrylate, epichlorohydrin homo and copolymers,propylene oxide rubber, fluorosilicone rubber, fluorocarbon rubber,chlorosulfonated polyethylene, chlorinated polyethylene,ethylene-propylene rubber, nitroso rubber and phosphonitrilic rubber.The properties of the sleeve are, to a large extent, dependent upon theintended use of the sleeve. Thus, if the sleeve is to be used primarilyas an electrical insulation, its electrical properties will be ofprimary importance. On the other hand, if the sleeve will be subjectedto much physical abuse, it may be necessary to provide a sleeve whichhas strength, good flame resistance, good solvent resistance, etc. Forhigh voltage uses, it may be desirable to have a sleeve which has beenmade semi-conductive by dispersing large amounts of suitable fillers orconductive particles in the sleeve or possesses resistance to trackingand/or erosion.

To some extent, the nature of the sleeve is dependent upon the nature ofthe restraint as is readily apparent to those skilled in the part. Thus,the force of recovery exerted by the expanded elastomeric sleeve cannotexceed either the strength of the restraint or of the bond between thesleeve and the restraint. Further, it is necessary to choose a sleevewhich is compatible with the restraint to the extent that it can bebonded to the restraint. These and other aspects of the relationshipbetween the sleeve, the adhesive and the restraint will become clear inthe discussion of the invention set forth below.

The Restraint

According to the present invention, the recoverable sleeve 2 is held inits extended or stretched condition by external tubular restraint 1.This restraint is depicted in FIG. 1 as being a tube having a circularcross section. However, any tubular article, i.e., an article at least aportion of which is closed in cross section, may be employed.

The restraint may be made of any suitable material such as rigidpolymeric material, metal, ceramic, wood or wood products such as paper,resin reinforced or impregnated paper, etc. In general, it is necessaryonly to use a material having sufficient strength to hold therecoverable material in its extended condition without being deformed orcollapsed and that it be capable of being segmented and peeled from therecoverable sleeve.

Prior to segmenting the only point at which peeling can be initiated isthe circular edge of the restraint. Further, when the restraint is inits unsegmented monolithic form it is not possible to apply force to therestraint to peel it away from the recoverable sleeve. Segmenting thusmakes it possible to remove the restraint by applying a peeling force toit and provides a greatly increased edge area at which peeling of therestraint from the sleeve can be initiated.

It is further desirable that the restraint be capable of being readilybonded to the recoverable sleeve so that it will hold the recoverablesleeve in its extended condition. The bond may be formed by adhesiondirectly between the sleeve and the restraint or by bonding the sleeveand restraint with an adhesive.

Particularly suitable outer restraints of polymeric material include anyrigid thermoplastic including polyvinyl chloride, polyethylene andcross-linked polyethylene, polystyrene, copolymers of styrene such ascopolymer of styrene and acrylonitrile, ABS polymer, etc.

Metallic outer restraints such as steel, tin, aluminum, etc., are alsoespecially suitable for this invention.

The restraint may be segmented by various means such as shattering therestraint by impact, tearing the restraint, e.g., along serrations orscores, cutting, etc.

A particularly convenient means of forming a removable restraint is toform the restraint from a frangible material such as polyvinyl chloridewhich will fracture when given a sharp blow. Thus, the polyvinylchloride restraint can simply be given a blow with a hammer causing itto shatter and become segmented making it possible to apply force topeel away the segments allowing the recoverable sleeve to recover onto asubstrate. FIGS. 2 and 3 illustrate this procedure. As shown in FIG. 2,the restraint 1 is shattered along fracture lines 4 to form smallsegments 5. Upon application of a peeling force such as scraping therestraint segments are peeled away allowing the sleeve to shrink asshown in FIG. 3. The segments may be removed by weakening the bondbetween the sleeve and the restraint, e.g., attacking the bond with asolvent to eliminate the necessity of applying a peeling force.

FIG. 4 is illustrative of a segmentable metallic outer restraint. There,outer metallic restraint 1 is scored or serrated or in some other wayweakened along the lines 6. The restraint can be simultaneouslysegmented and removed by peeling it off along the weakened lines 6. Forconvenience, a pullring 7 of the type supplied on beverage cans may beprovided.

To facilitate peeling of the segments, the outer surface of therestraint may contain means for applying a peeling force such as thepullring 7 or other grippable projections.

The Bond

The bond between the elastomeric sleeve and the outer restraint shouldbe sufficiently strong so that the bond will prevent separation of theexpanded elastomeric sleeve from the restraint under normal conditionsof storage and handling over a long period of time.

The bond may be formed simply by adhesion of the sleeve to the restraintwithout the use of any additional bonding agent. Such adhesion may occurwhen two polymeric materials are joined together, particularly at anelevated temperature such that they are both tacky. For example, inusing a polyvinyl chloride restraint for a neoprene elastomeric sleeve,it has been found convenient to injection mold the polyvinyl chloridearound the neoprene sleeve. At the injection molding temperatures, abond is formed between the polyvinyl chloride restraint and the neoprenesleeve.

It is frequently desirable to use adhesives to insure a suitable bondbetween the sleeve and the restraint. Any adhesive which will provide astrong enough bond to prevent premature recovery of the sleeve may beused.

In general, hot melt adhesives are preferred. A hot melt adhesive wouldnormally be applied by coating one or both surfaces with a solution ofthe adhesive, allowing the solvent to evaporate and then bringing thesurfaces together under the application of heat and pressure.

A preferred hot melt adhesive for neoprene-PVC is a multisegmented blockcopolymer comprising units of polytetraethylene ether andpolytetramethylene terephthalate. A polymer of this type is sold byDuPont under the trade name HYTREL. This adhesive forms a strong bondbetween neoprene and polyvinyl chloride. It has the additionaldisadvantage of being readily weakened by application of a number ofsolvents.

Various copolymers may be used as adhesives such as copolymers ofethylene vinyl acetate, e.g. ELVAX from DuPont copolymers ofethylene-ethylacrylate, etc. Terpolymers such as terpolymers ofethylene, vinyl acetate, and methacrylic acid may also be used. Theseadhesives may be used alone or with tackifiers.

Other hot melt adhesives suitable in the practice of this invention arepolyamide resin adhesives. Exemplary of such adhesives are thoseavailable from General Mills under the trade name VERSALON, polyesteradhesive, (see, e.g., DuPont Technical Bulletin No. 17--"PolyesterAdhesives") and the wide variety of polyvinyl, polybutene, andpolyacrylate adhesives with which the art is familiar.

Various rubber based adhesives such as those based upon silicone,nitrile, and neoprene may be used.

Preferably, the adhesive will have greater strength in tension than ithas in peel. The strength will prevent recovery during storage. When apeel force is applied during recovery the low peel strength makesrecovery possible without the necessity of applying a large force.

In general, any adhesive is suitable if it has good affinity for thesurface of the restraint and the sleeve and is resistant to creep underload. Preferably the adhesive is thermoplastic so that it will soften onheating to flow and ultimately wet the surface of both the restraint andsleeve.

Any suitable method of applying the adhesive to the surfaces of thesleeve and/or the restraint may be employed. A satisfactory method ofapplication is to apply the adhesive from solution to one or bothsurfaces and allow the solvent in the adhesive to evaporate, bringingthe surfaces together under the application of pressure and, if desired,heat to form a strong bond.

In one embodiment of this invention, the outer restraint is injectionmolded around the sleeve. In that case, the adhesive is applied to thesurface of the elastomeric sleeve prior to the time of injectionmolding. In general, it is desired that the peel strength of theadhesive bond be greater than 10 pounds per inch and preferably that thepeel strength be greater than 20 pounds per inch. However, there is noabsolute requirement with regard to peel strength. Thus, the importantconsideration is whether the peel strength is sufficient to prevent thesleeve from peeling away from the restraint during storage or at anytime prior to the time when it is desired to shrink the sleeve downabout the substrate. Of course it is within the scope of this inventionto provide an inner restraining core, e.g., a cardboard tube, to preventpremature recovery. If the force tending to cause the sleeve to shrinkand peel away from the restraint is not great, a high peel strength isnot so necessary. On the other hand, if a sleeve having an extremelyhigh retractive force is employed, it is necessary to use an adhesivewhich will form a bond having a high peel strength.

Internal Coating

The recoverable sleeve may be coated on its internal surface withvarious materials for contacting the substrate. Thus, an adhesive mayadvantageously be applied to the interior surface of the recoverablesleeve so that the sleeve will form a bond with a substrate about whichis recovered. Because the recoverable sleeve of this invention does notrequire heat for its recovery, it is preferred to employ an adhesivewhich does not require the application of heat to form a strong bondwith a substrate. In this regard, various contact or pressure sensitiveadhesives may be employed.

In addition to adhesives, various other materials may be employed on theinternal surface of the recoverable sleeve. For example, materials ofthe type described in U.S. Pat. No. 3,396,460 may be used. In manyinstances, it is desired to coat the inside of the sleeve with materialswhich will flow under the application of pressure at the temperature ofapplication. Preferably, these materials will adhere to both the sleeveand the substrate. Particularly suitable materials for this applicationare mastic and mastic-like materials.

The recoverable article of the present invention has a wide range ofapplications. Thus, it can be used for any application in which heatrecoverable sleeves are normally used. For example, it can be used forinsulating splices in electrical conductors in both low and high voltageapplications. The article may be used for covering repairs or joints inelectronic equipment. The sleeves are particularly suitable for use incovering splices and repairs in telephone cables and cable TV lines.

An area where heat recoverable sleeves have had a great deal of use inrecent years is for the repairing of splices in electrical cables usedin mines. The sleeves of the present invention are particularly suitablefor such mine cable splices because they do not require the applicationof heat which is usually accomplished by the use of a torch. This may bea major advantage, particularly in gassy mines where torches presentgreat safety dangers.

Fabrication Procedures

A number of methods are available for manufacturing the articles of thisinvention. Simply stated, the articles can be formed by bonding thesleeve, in the expanded or extended state, to an outer restraint. Oneconvenient method of accomplishing this is to form an outer restraint ofthe desired size and an elastomeric sleeve of the desired finaldiameter. Then, the inner surface of the restraint and the outer surfaceof the elastomeric sleeve are coated with a suitable adhesive and theelastomeric sleeve is expanded into contact with the restraint byinternal air pressure, a mandrel, etc. The sleeve is held in contactwith the restraint for a period of time sufficient for a bond to beformed whereupon the mandrel or internal pressure is removed.

Another technique for forming the article comprises first forming thesleeve and then injection molding the outer restraint around the sleeve.In this method, the sleeve is first coated with adhesive. Then, theouter restraint material is injection molded around the sleeve. Beforethe restraint has hardened on cooling, the restraint and sleeve areexpanded by a mandrel or compressed air to give the desired expansionand desired final inside diameter to the sleeve. While the sleeve is inthe expanded condition, the restraint is cooled and hardened and uponremoval of the mandrel or release of the air pressure, the sleeveremains bonded to the restraint and held in the expanded condition.

The injection molding process described above has been found to beparticularly suitable for use with a combination of a neoprene sleeve, aHYTREL adhesive, and a polyvinyl chloride restraint. However, it will bereadily obvious that the process can be carried out using a wide rangeof suitable materials.

As indicated herein, a wide variety of materials may be used tomanufacture the article of the present invention depending upon thedesired properties of the article. In the case of mine splices, it isnecessary to provide a recoverable sleeve which has great strength andabrasion resistance in the recovered state. These requirements aredictated by the mechanical abuse which mine cables must survive. Thus,properties such as tensile strength, elongation, flammability, abrasionresistance, and dielectric strength are all important considerations forsuch sleeves. Additionally, it is important that the sleeves resistpeeling or creeping away from the splice which they cover. Typically,mine sleeves are wound on and off cable reels in the mines, are pulledover sharp rock surfaces, and are frequently exposed to impact againstsharp edges.

It has been found that a combination of materials used in accordancewith this invention will provide a recoverable article having propertiessufficient for use in the extremely demanding environment of the mine.In particular, a recoverable elastomeric mine sleeve requires anextremely high recovery force and thus it has been necessary to providea restraint and adhesive which will provide a strong bond between therestraint and sleeve to maintain the sleeve in the desired extendedcondition until recovery is desired.

According to the present invention, an elastomeric sleeve having a goodcombination of properties and being suitable for use as a mine splicesleeve comprises a neoprene sleeve having either of the followingcompositions:

                  TABLE I                                                         ______________________________________                                                              Parts By Weight                                         Component               A        B                                            ______________________________________                                        Neoprene rubber         100      100                                          Phenyl-alpha-naphthlamine                                                                             2        2                                            Magnesium Oxide         1        1                                            Stearic acid            0.5      0.5                                          HAF Carbon Black        5        5                                            Hydrated alumina        10       10                                           Precipitated Silica     15       15                                           Antimony oxide          15       15                                           Tri (Z--ethylhexyl) phosphate                                                                         4        4                                            Zinc oxide              5        5                                            N--Cyclohexyl-2-benzothiazole sulfeamide                                                              1        0.75                                         A treated amine sold by DuPont as TA-11                                                               2        --                                           Tetramethyl thiourea    --       0.75                                         ______________________________________                                    

When cured at 350° F. for 15 minutes, a slab 0.075 in. thick and a tubehaving an inside diameter of 0.75 in. and an outside diameter of 1.0 in.from these compositions were found to have the following properties:

                  TABLE II                                                        ______________________________________                                                            A     B                                                   ______________________________________                                        SLAB PROPERTIES                                                               Tensile Strength, psi 4400    3000                                            Ultimate Elongation, %                                                                              710     650                                             Tensile Stress at:                                                            100% Elong.           290     260                                             200% Elong.           650     385                                             300% Elong.           1150    610                                             TUBE PROPERTIES                                                               Tensile Strength, psi 1990    970                                             Ultimate Elongation, %                                                                              510     430                                             Tensile Stress at:                                                            100% Elong., psi      250     230                                             200% Elong., psi      460     330                                             300% Elong., psi      850     500                                             Tensile Strength at 150° C., psi                                                             370     280                                             Ultimate Elongation at 150° C., %                                                            200     150                                             Tear Strength (Die C), pli                                                                          370     215                                             Tear Strength (Die C) at:                                                                            90      80                                             150° C., pli                                                           Tape Abrasion (1/4" strip,                                                                           35      36                                             250" tape, 2 lb. wt.,                                                         1504 Grid, mil)                                                               Tensile Set (200% elong. at RT)                                               After 24 hrs., %       1       2                                              After 7 days, %        6       10                                             ______________________________________                                    

Using the compositions of Table I, tubes of neoprene having an i.d. of0.75 in. and an o.d. of 1.0 in. were molded. The neoprene tubes wereplaced in an injection mold and a polyvinyl chloride composition as setforth below in Table III was injected around it. Two suitable polyvinylchloride compositions are as follows:

                  TABLE III                                                       ______________________________________                                        Component              A       B                                              ______________________________________                                        Polyvinylchloride      100     100                                            An organotin stabilizer sold                                                                         3       3                                              by M & T Chemicals                                                            A cycloaliphatic epoxy sold                                                                          4       4                                              by Ciba-Geigy                                                                 Low molecular weight polyethylene                                                                    2       2                                              Low nolecular weight nitrile rubber                                                                  10      --                                             ______________________________________                                    

Prior to the injection of the polyvinyl chloride, the outer surface ofthe neoprene sleeve was abraded and coated with a 5% solution of HYTRELin chloroform and dried. Prior to injection molding, the tubes werepreheated to soften the adhesive. Injection Molding Machine using theconditions set forth in Table IV, below:

                  TABLE IV                                                        ______________________________________                                        Machine Temperature                                                           Nozzle heat, °F.                                                                           390                                                       Front heat, °F.                                                                            375                                                       Center heat, °F.                                                                           365                                                       Rear heat, °F.                                                                             300                                                       Mold Temperature                                                              Manifold, °F.                                                                              275                                                       Front plate, °F.                                                                           175                                                       Back plate, °F.                                                                            200                                                       Machine Settings                                                              Injection time, seconds                                                                            15                                                       Cooling time, seconds                                                                              15                                                       Total cycle time, seconds                                                                         60-90                                                     ______________________________________                                    

The resulting tubular article was expanded by preheating the tube andexpanding 100 to 200% using air pressure to expand the tube into a coldexpansion mold. The peel strength was found to be about 40 lb/in.between the polyvinyl chloride restraint and the neoprene sleeve.

The tube was recovered by fracturing the restraint with a hammer andallowing the sleeve to recover onto a substrate.

The tubular articles of this invention may be expanded using theapparatus and method described in Greuel application Ser. No. 436,675entitled EXPANSION APPARATUS AND PROCESS and filed Jan. 25, 1974 (nowabandoned).

It is to be understood that the foregoing examples are merelyillustrative of the invention and that the scope is not limited to theseexemplary embodiments of the invention. For example, metallic restraintsmay be used with suitable adhesive to bond the metal and elastomer.Thus, the scope of the invention is limited only by the scope of theappended claims.

We claim:
 1. The method of covering a member comprising:positioning oversaid member a recoverable tubular article comprising: (a) a tubularsleeve held under tension in a radially expanded condition such thatupon the release of the tension the sleeve tends to assume a smallerdiameter and (b) a restraint having an essentially tubular configurationbonded to said sleeve; segmenting said restraint and peeling saidrestraint from said sleeve to allow recovery of said sleeve onto saidmember.
 2. The method of claim 1 wherein the restraint comprises afrangible material.
 3. The method of claim 1 wherein the restraint is ametallic restraint having weakened portions so that it can be segmentedat the weakened portions.
 4. The method of claim 1 wherein saidrestraint is a plastic or metallic tube having helical scores on itsouter surface.
 5. A method of covering a member which methodcomprises:(a) positioning over said member a recoverable tubular sleevewhich is held in a radially expanded condition by applying to saidsleeve restraint forces applied by a tubular restraint which surroundsthe recoverable tubular sleeve and is substantially concentrictherewith; and (b) releasing the restraint forces by segmenting thetubular restraint.
 6. A method of covering a member which methodcomprises:(a) positioning over said member a recoverable tubular sleevewhich is held in a radially expanded condition by applying to saidsleeve restraint forces applied by a tubular restraint which surroundsthe recoverable tubular sleeve and is substantially concentrictherewith; and (b) releasing the restraint forces by segmenting thetubular restraint and then removing one or more of the segments of thetubular restraint.
 7. A method of covering a member, which methodcomprises:(a) surrounding the member with a recoverable tubular sleevewhich is held in a radially expanded form by an external restrainingmeans; and (b) causing the recoverable tubular sleeve to decrease indirection by segmenting the restraining means such that the tubularsleeve only comes into contact with the member to be covered.